The present invention relates to video keyers, and more particularly to a non-linear keyer for increasing the selectivity of a key control signal used to insert key fill video into a background video by modifying the key processor transfer function.
In a traditional keyer there is a problem with setting the clip level since there are many times when more selectivity is desired above or below the clip level. Varying the gain helps, but the result often appears compromised. A high gain gives good selectivity to exclude some unwanted part of a key source, but can give harsh edges to the key control signal.
What is desired is a non-linear keyer that can vary the gain independently above and below the clip level.